Fuel injection device for an internal combustion engine

ABSTRACT

A fuel injection apparatus having at least one solenoid valve for controlling the fuel injection that is contained in a housing part and a solenoid assembly having a magnetic coil and a magnet armature inserted into a recess of the housing part. A cover piece that can be attached to the housing part fixes the solenoid assembly in the housing part. A spring element is disposed between the cover piece and the solenoid assembly and clamps the solenoid assembly in the housing part. At least one securing element is formed onto the spring element and is of one piece with it, which secures the spring element to the housing part and secures the solenoid assembly in the recess of the housing part without the cover piece being attached to the housing part.

PRIOR ART

The invention is based on a fuel injection apparatus for an internalcombustion engine as generically defined by the preamble to claim 1.

A fuel injection apparatus of this kind is known from the literature,for example from Diesel Motor Management, Verlag Vieweg, 2^(nd) edition,1998, p. 246. This fuel injection apparatus has a solenoid valve forcontrolling the fuel injection. The solenoid valve is inserted into ahousing part and has a solenoid assembly with a magnetic coil and amagnet armature. The housing part has a cover piece attached to it thatholds the solenoid assembly of the solenoid valve in the housing part.With the insertion of the solenoid assembly into the housing part, theproblem arises that the solenoid assembly is only fixed in place whenthe cover piece is attached to the housing part so that beforeattachment of the cover piece, the solenoid assembly can fall back outof the housing part. In order to avoid unnecessary assembly steps, thecover piece should preferably be attached to the housing part only afterthe function of the solenoid assembly has been tested, but there is thedanger that the solenoid assembly will fall out during the functiontesting. Furthermore, in this known fuel injection apparatus, it is notpossible to compensate for different lengths of the solenoid assembly sothat in some cases, it is not fixed securely in the housing part.

ADVANTAGES OF THE INVENTION

The fuel injection apparatus according to the invention, with thecharacterizing features of claim 1, has the advantage over the prior artthat the solenoid assembly is fixed in the housing part before theattachment of the cover piece. In addition, the spring element makes itpossible to compensate for the length of the solenoid assembly andtherefore permits it to be securely fixed. The embodiment of the atleast one securing element so that it is of one piece with the springelement means that only one additional component is required.

Advantageous embodiments and modifications of the fuel injectionapparatus according to the invention are disclosed in the dependentclaims. With the embodiment of the spring element in the form of a discspring according to claim 2, it requires only a small amount of space.The embodiment according to claim 3 and 4 permits a secure fixing of thespring element and therefore also of the solenoid assembly.

DRAWINGS

Several exemplary embodiments of the invention are shown in the drawingsand will be explained in detail in the subsequent description.

FIG. 1 shows a detail of the fuel injection apparatus for an internalcombustion engine with a solenoid valve,

FIG. 2 shows a longitudinal section through a housing part of the fuelinjection apparatus according to FIG. 1 with a spring element accordingto a first exemplary embodiment,

FIG. 3 shows a perspective view of the spring element according to thefirst exemplary embodiment,

FIG. 4 shows a perspective view of the housing part with the springelement according to the first exemplary embodiment,

FIG. 5 shows a perspective view of the spring element according to asecond exemplary embodiment, and

FIG. 6 shows a detail of the housing part with the spring elementaccording to the second exemplary embodiment.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a schematic depiction of a fuel injection apparatus for aninternal combustion engine, for example of a motor vehicle. The engineis preferably an autoignition engine and has one or more cylinders. Thefuel injection apparatus can be embodied, for example as shown in FIG.1, in the form of a unit injector that has a high-pressure fuel pump 10and a fuel injection valve 12 for each cylinder of the engine, which areincorporated into a common component. The unit injector is provided withat least one solenoid valve 56, 60 for controlling the fuel injection.Alternatively, the fuel injection apparatus can also be embodied as aunit pump in which a high-pressure fuel pump and a fuel injection valveare likewise provided for each cylinder of the engine, but are separatefrom each other and are connected to each other via a hydraulic line.The high-pressure fuel pump or the fuel injection valve of the unit pumpis provided with a solenoid valve for controlling the fuel injection.Furthermore, the fuel injection apparatus can also be embodied as acommon rail system in which a high-pressure fuel pump supplies fuel intoa reservoir that is connected to injectors provided at the cylinders ofthe engine, each of which is provided with a solenoid valve forcontrolling the fuel injection. Moreover, the fuel injection apparatuscan also be embodied as a fuel injection pump that supplies highlypressurized fuel and is connected to the fuel injection valves providedat the cylinders of the engine; the fuel injection pump is provided witha solenoid valve for controlling the high-pressure generation andtherefore the fuel injection.

The invention will be explained below in conjunction with its use in aunit injector, but it can also be transferred to the above-mentionedother embodiments of fuel injection apparatuses. The high-pressure fuelpump 10 has a pump piston 20, which is guided in a sealed fashion in acylinder bore 16 of a pump body 18 and defines a pump working chamber 22in the cylinder bore 16. A cam 24 of a camshaft of the engine sets thepump piston 20 into a stroke motion at least indirectly, for example viaa rocker, counter to the force of a return spring 26. A fuel-supply pump29, for example, supplies fuel from a fuel tank 28 to the pump workingchamber 22 during the intake stroke of the pump piston 20.

The fuel injection valve 12 has a valve body 30, which is connected tothe pump body 18, can be composed of a number of parts, and contains abore 32 in which an injection valve element 34 is guided so that it canslide longitudinally in a sealed fashion. An intermediate body 36 isdisposed between the valve body 30 and the pump body 18. In its endregion oriented toward the combustion chamber of the engine cylinder,the valve body 30 has at least one, preferably several injectionopenings 38. The injection valve element 34, in its end region orientedtoward the combustion chamber, has a for example conical sealing surface42 that cooperates with a valve seat 41 embodied in the end region ofthe valve body 30 oriented toward the combustion chamber; the injectionopenings 32 branch off from this valve seat 41 or branch off downstreamof it. Between the injection valve element 34 and the bore 32 leading tothe valve seat 41, the valve body 30 contains an annular chamber 42,whose end region oriented away from the valve seat 41, by means of aradial expansion of the bore 32, transitions into a pressure chamber 44encompassing the injection valve element 34. At the same level as apressure chamber 44, the injection valve element 34 has a pressureshoulder 46, which is oriented toward the valve seat 41 and is formed bya cross-sectional change. A prestressed closing spring 48 engages theend of the injection valve element 34 oriented away from the combustionchamber and pushes the injection valve element 34 toward the valve seat41. The closing spring 48 is disposed in a spring chamber 49 that iscontained in the valve body 30 or in the intermediate body 36 andadjoins the bore 30.

The end of the spring chamber 49 oriented away from the pressure chamber44 adjoins a bore 50 with a smaller diameter. A control piston 51 isguided in a sealed fashion in the bore 50 and delimits a controlpressure chamber 52 in the bore 50. The control piston 51 rests againstthe injection valve element 34 and, depending on the pressure prevailingin the control pressure chamber 52, generates a force in the closingdirection on the injection valve element 34 that boosts the action ofthe closing spring 48. From the pump working chamber 22, a conduit 54leads through the pump body 16, the intermediate body 36, and the valvebody 30, into the pressure chamber 44 of the fuel injection valve 12.From the conduit 54, a connection 55 leads to the fuel-supply pump 29and to the fuel tank 28. A first solenoid valve 56 embodied as a 2/2-wayvalve controls the connection 55. An electronic control unit 57 thatwill be described in more detail below triggers the solenoid valve 56.Another conduit 58 leads from the conduit 54 into the control pressurechamber 52 and the control pressure chamber 52 has a connection 59 to adischarge region, for example a return into the fuel tank 28. Thecontrol unit 57 also triggers a second solenoid valve 60 that controlsthe connection 59 of the control pressure chamber 52 to the dischargeregion. The first solenoid valve 56 controls the pressure buildup in thepump working chamber 22 of the high-pressure fuel pump 10 and the secondsolenoid valve 60 controls the pressure in the control pressure chamber52 and therefore controls the opening of the fuel injection valve 12.The second solenoid valve 60 and the control pressure chamber 52 canalso be omitted, in which case the closing spring 48 alone determinesthe opening of the fuel injection valve 12. If the pressure prevailingin the pressure chamber 44 and acting on the pressure shoulder 46 exertsa greater force on the injection valve element 34 than the closingspring 48 and the pressure prevailing in the control pressure chamber52, then the injection valve element 34 moves in the opening direction35 and unblocks the injection openings 38.

FIG. 2 shows an enlargement of the intermediate body 36, with the twosolenoid valves 56 and 60 contained in it. The intermediate body 36 hastwo recesses 61 leading from its end surface oriented toward the pumpbody 16, each of which has a solenoid assembly 62 of the respectivesolenoid valves 56, 60 inserted into it. Each solenoid assembly 62 has amagnetic coil 63 and a magnet armature 64 and may also include othercomponents. Toward the open end of the recesses 61, a respectivepressure piece 65 covers each of the solenoid assemblies 62. The crosssections of the recesses 61 and the solenoid assemblies 62 are matchedto one another, for example are circular. Each magnet armature 64 isconnected to a respective solenoid valve element 66 that opens or closesthe connection 55 between the conduit 50 and the fuel-supply pump 29 orthat opens or closes the connection 59 between the control pressurechamber 52 and the discharge region. When the magnetic coil 63 iswithout current, the solenoid valve element 66 of the respectivesolenoid valve 56, 60 is disposed in a first position in which it hasopened or closed the connection 55, 59 and when the magnetic coil 63 issupplied with current, the solenoid valve element 66 of the respectivesolenoid valve 56, 60 is moved into a second position in which itcorrespondingly closes or opens the connection 55, 59.

In a first exemplary embodiment shown in FIGS. 2 to 4, the solenoidassemblies 62 of the two solenoid valves 56, 60 are each secured in therecesses 61 by a respective spring element 70. A spring element 70embodied in the form of a round disc spring is provided for eachsolenoid assembly 62 and, via the respective pressure piece 65, clampsthe solenoid assembly 62 in the recess 61 in an axial direction, i.e. inthe direction of the longitudinal axis of the recess 61 and of thesolenoid assembly 62. The two spring elements 70 here are embodied asbeing of one piece with each other and are connected to each other via abridge piece 71 shown in FIG. 3. The spring elements 70 are curved inthe axial direction in order to produce the required clamping action.The spring elements 70 also have securing elements that are formed ontothem and are of one piece with them, which permit the spring elements 70to be affixed to the intermediate body 36 and will be described in moredetail below. One of the spring elements 70 has a securing element 72 inthe form of a hook formed onto it. The hook 72 protrudes approximatelyradially out from the spring element 70 and its free end is curvedinward into a U-shape. The hook 72 is preferably embodied as flexibleand engages the intermediate body 36 at least indirectly. A pin 74 thatextends at least approximately parallel to the longitudinal axes of therecesses 61 is press-fitted into the end of the intermediate body 36oriented toward the pump body 16. The hook 72 of the spring element 70is hooked onto the pin 74 and encompasses the part of it that protrudesfrom the intermediate body 36. Alternatively, the hook 72 can also bepress-fitted onto the pin 74. The other spring element 70 has anothersecuring element that is formed onto it and of one piece with it, whichis comprised of two lugs 75 that are offset from each other in thecircumference direction and engage the intermediate body 36 at leastindirectly. The lugs 75 laterally embrace another pin 76 that ispress-fitted into the intermediate body 36. The end of the intermediatebody 36 oriented toward the pump body of 16 is provided withindentations for the securing elements 72 and 75 and for the bridgepiece 71 connecting the two spring elements 70 so that they do notprotrude out from the end surface of the intermediate body 36.

When the spring elements 70 are inserted into the recesses 61, the hook72 encompasses the pin 74 or is press-fitted onto the pin 74 and thelugs 75 embrace the pin 76, thus producing a clamped connection betweenthe spring elements 70 and the pins 74, 76 so that the spring elementscan no longer fall out of the intermediate body 36. The spring elements70 consequently fix the solenoid assemblies 62 of the solenoid valves56, 60 in the intermediate body 36 so that they cannot fall out. It istherefore possible to test the function of the solenoid assemblies 62 ofthe solenoid valves 56, 60 inserted into the recesses 61 of theintermediate body 36, without the danger of the solenoid assemblies 62falling out. The spring elements 70 also prevent the solenoid assemblies62 inserted into the intermediate body 36 from falling out duringsubsequent transport before final assembly of the fuel injectionapparatus. During subsequent assembly of the fuel injection apparatus,the pump body 16 and the valve body 30 are fitted together with theintermediate body 36; the pump body 16 constitutes a cover piece thataxially compresses the spring elements 70 and by means of them, clampsthe solenoid assemblies 62 into the recesses 61 of the intermediate body36, consequently fixing them without play.

FIGS. 5 and 6 show a second exemplary embodiment of the spring element170. In this case, only one spring element 170 is provided for one ofthe solenoid valves 56, 60. It is possible here that only the firstsolenoid valve 56 and a spring element 170 for it are provided or thattwo solenoid valves 56, 60 are provided, each with a separate springelement 170. The spring element 170 is embodied as a disc spring with acircular cross section and, encompassing this disc spring, a retainingelement 172 in the form of a securing ring that is formed onto it and ofone piece with it. The securing ring 172 is formed onto the springelement 170, attached by a bridge piece 171 extending approximately inthe radial direction. The securing ring 172 is designed so that it canbe deformed elastically in the radial direction. Close to its endoriented toward the end surface of the intermediate body 136, thecircumference of the recess 161 in the intermediate body 136 into whichthe solenoid assembly 62 is inserted has a cross-sectional enlargement174 that forms an undercut and that can be constituted by an annulargroove, an indentation, or a bore, into which the securing ring 172 canexpand radially outward, engaging it in detent fashion. When relaxed,the diameter of the securing ring 172 is slightly greater than thediameter of the recess 161; when the spring element 170 is inserted intothe recess 161, the securing ring 172 is elastically compressed in theradial direction and in the end position of the spring element 170,relaxes outward, engaging in the annular groove 174 in detent fashion.This fixes the spring element 170 to the intermediate body 136 and thusprevents the solenoid assembly 62 from falling out of the intermediatebody 136. When the pump body 16 is fitted as a cover piece onto theintermediate body 136, the spring element 170 is compressed in the axialdirection and thus secures the solenoid assemblies 62 in theintermediate body 136 without play.

1-10. (canceled)
 11. A fuel injection apparatus for an internalcombustion engine, the apparatus comprising a housing part (36; 136) atleast one solenoid valve (56, 60) inserted into the housing part (36;136) and operable for controlling the fuel injection, the solenoid valve(56, 60) including a solenoid assembly (62), which has a magnetic coil(63) and a magnet armature (64) and which is inserted into a recess (61)of the housing part (36; 136), a cover piece (16) attaching the solenoidassembly (62) to and fixing the solenoid assembly (62) in the housingpart (36; 136), a spring element (70; 170) disposed between the coverpiece (16) and the solenoid assembly (62) and clamping the solenoidassembly (62) in the housing part (36; 136), and at least one securingelement (72, 74; 172) formed onto and of one piece with the springelement (70; 170) securing the spring element (70; 170) to the housingpart (36; 136) and secures the solenoid assembly (62) in the recess (61)of the housing part (36; 136), prior to the cover piece (16) beingattached to the housing part (36; 136).
 12. The fuel injection apparatusaccording to claim 11, wherein the spring element (70; 170) is embodiedas a disc spring.
 13. The fuel injection apparatus according to claim11, wherein the at least one securing element (170) is embodied as aradially elastic securing ring that encompasses the spring element (170)and can engage with the housing part (136) in detent fashion.
 14. Thefuel injection apparatus according to claim 12, wherein the at least onesecuring element (170) is embodied as a radially elastic securing ringthat encompasses the spring element (170) and can engage with thehousing part (136) in detent fashion.
 15. The fuel injection apparatusaccording to claim 13, wherein the circumference of the recess (161) inthe housing part (136) is provided with an undercut (174) in which thesecuring ring (172) can engage in detent fashion.
 16. The fuel injectionapparatus according to claim 14, wherein the circumference of the recess(161) in the housing part (136) is provided with an undercut (174) inwhich the securing ring (172) can engage in detent fashion.
 17. The fuelinjection apparatus according to claim 11, wherein the at least onesecuring element (72) is embodied as a hook that protrudes out from thespring element (70), preferably at least approximately in the radialdirection, and adapted to be hooked at least indirectly to the housingpart (36).
 18. The fuel injection apparatus according to claim 12,wherein the at least one securing element (72) is embodied as a hookthat protrudes out from the spring element (70), preferably at leastapproximately in the radial direction, and adapted to be hooked at leastindirectly to the housing part (36).
 19. The fuel injection apparatusaccording to claim 17, wherein the apparatus further comprises a pin(74) fastened to the housing part (36), and wherein the hook (72) can behooked onto or press-fitted onto the pin (74).
 20. The fuel injectionapparatus according to claim 18, wherein the apparatus further comprisesa pin (74) fastened to the housing part (36), and wherein the hook (72)can be hooked onto or press-fitted onto the pin (74).
 21. The fuelinjection apparatus according to claim 11, wherein the at least onesecuring element (75) is comprised of two lugs that are spaced apartfrom each other and protrude out from the circumference of the springelement (70), preferably at least approximately in the radial direction,and preferably embrace a pin fastened to the housing part (36) or can bepress-fitted onto the pin.
 22. The fuel injection apparatus according toclaim 12, wherein the at least one securing element (75) is comprised oftwo lugs that are spaced apart from each other and protrude out from thecircumference of the spring element (70), preferably at leastapproximately in the radial direction, and preferably embrace a pinfastened to the housing part (36) or can be press-fitted onto the pin.23. The fuel injection apparatus according to claim 17, wherein the atleast one securing element (75) is comprised of two lugs that are spacedapart from each other and protrude out from the circumference of thespring element (70), preferably at least approximately in the radialdirection, and preferably embrace a pin fastened to the housing part(36) or can be press-fitted onto the pin.
 24. The fuel injectionapparatus according to claim 19, wherein the at least one securingelement (75) is comprised of two lugs that are spaced apart from eachother and protrude out from the circumference of the spring element(70), preferably at least approximately in the radial direction, andpreferably embrace a pin fastened to the housing part (36) or can bepress-fitted onto the pin.
 25. The fuel injection apparatus according toclaim 17, wherein the at least one securing element (75) is comprised oftwo lugs that are spaced apart from each other and protrude out from thecircumference of the spring element (70), preferably at leastapproximately in the radial direction, and preferably embrace a pinfastened to the housing part (36) or can be press-fitted onto the pin,and wherein a securing element comprised of the hook (72) and a securingelement comprised of the lugs (75) are formed onto the spring element(70) and in that the securing elements (72, 75) are disposed offset fromeach other in the circumference direction on the spring element (70).26. The fuel injection apparatus according to claim 19, wherein the atleast one securing element (75) is comprised of two lugs that are spacedapart from each other and protrude out from the circumference of thespring element (70), preferably at least approximately in the radialdirection, and preferably embrace a pin fastened to the housing part(36) or can be press-fitted onto the pin, and wherein a securing elementcomprised of the hook (72) and a securing element comprised of the lugs(75) are formed onto the spring element (70) and in that the securingelements (72, 75) are disposed offset from each other in thecircumference direction on the spring element (70).
 27. The fuelinjection apparatus according to claim 25, wherein two solenoid valves(56, 60) are provided that each have a respective solenoid assembly (62)inserted into a recess (61) in the housing part (36), wherein eachsolenoid assembly (62) is associated with a spring element (70), andwherein the two spring elements (70) are embodied as being of one piecewith each other.
 28. The fuel injection apparatus according to claim 26,wherein two solenoid valves (56, 60) are provided that each have arespective solenoid assembly (62) inserted into a recess (61) in thehousing part (36), wherein each solenoid assembly (62) is associatedwith a spring element (70), and wherein the two spring elements (70) areembodied as being of one piece with each other.
 29. The fuel injectionapparatus according to claim 27, wherein a securing element comprised ofthe hook (72) is formed onto the one spring element (70) and a securingelement comprised of the lugs (75) is formed onto the other springelement (70).
 30. The fuel injection apparatus according to claim 28,wherein a securing element comprised of the hook (72) is formed onto theone spring element (70) and a securing element comprised of the lugs(75) is formed onto the other spring element (70).